Process control systems use a variety of field devices to control and/or monitor process parameters. Field devices, such as fluid control valves, control the flow of fluid through a passageway of a valve. A control valve typically employs an actuator to move a flow control member relative to an orifice of the valve to allow fluid flow through the passageway of the valve and to restrict or prevent fluid flow through the passageway of the valve. The actuator is operatively coupled to the flow control member via a valve stem.
Some process control devices often include seals to prevent fluid leakage. For example, some known fluid valves employ a bellows-type seal to prevent fluid leakage to the environment along the valve stem. However, the seals (e.g., bellows seals) are often subjected to stresses during operation that can significantly reduce the operating life of the seal. For example, fluid flowing through the passageway of the valve body may impart torsion loads to a bellows-type seal. Such torsion loads may significantly reduce the cycle life of the bellows-type seal.